Optical microdevice with rotatable microactuator

ABSTRACT

An optical microswitch comprising a support body and first and second output fibers carried by the body. A rotary electrostatic microactuator is carried by the body and extends in a plane. A micromirror is disposed out of the plane. The microactuator has a mirror holder coupled to the micromirror and at least one comb drive assembly coupled to the mirror holder for driving the micromirror about an axis of rotation extending perpendicular to the plane between a first position for reflecting a laser beam to the first output fiber and a second position for reflecting the laser beam to the second output fiber.

CROSS-REFERENCE TO RELATED APPLICATION

[0001] The application claims priority to U.S. provisional patentapplication Serial No. 60/112,263 filed Dec. 15, 1998 and to U.S.provisional patent application Serial No. 60/123,512 filed Mar. 8, 1999,the entire contents of each of which are incorporated herein by thisreference.

SCOPE OF THE INVENTION

[0002] The present invention relates generally to optical microswitchesand more particularly to optical microswitches utilizing electrostaticmicroactuators with comb drive assemblies.

BACKGROUND

[0003] Optical switches have heretofore been provided. Many of suchswitches use macroscopic rotators. Switches utilizing electromagneticmotors have been disclosed to move either an input optical fiber or arefractive or reflective element interspersed between input and outputoptical fibers. Examples of such designs that use piezoelectric elementsto move refractive or reflective elements are shown in U.S. Pat. No.5,647,033 to Laughlin, U.S. Pat. No. 5,748,813 to Buchin and U.S. Pat.No. 5,742,712 to Pan et al. All of switches are relatively large andexpensive.

[0004] A micromachined optical switch is disclosed in U.S. Pat. No.5,446,811 to Field et al. and uses a bimetallic element to displace anoptical fiber into alignment with one or more optical fibers. Suchswitch, however, is not easily extendable to a switch having arelatively large number of output fibers and bimetallic actuators arerelatively slow.

[0005] Micromachined devices to tilt or rotate mirrors are known in theprior art, but suffer from various limitations. A one dimensional or twodimensional mirror rotator that tilts about axes in the plane of thesubstrate used to fabricate the device is disclosed in Dhuler et al., “ANovel Two Axis Actuator for High Speed Large Angular Rotation”,Transducers '97, Vol. 1, pp. 327-330. The actuator uses a variable gapparallel plate capacitor as the drive element, which suffers fromnon-linear response of force or angular displacement as a function ofapplied voltage. A similar type of tilting mirror is described in Kruthet al., “Silicon Mirrors and Micromirror Arrays for Spatial Laser BeamModulation”, Sensors and Actuators A 66 (1998), pp. 76-82. Such mirrorsare typically designed for use in projection displays or in scanners forbar code reading. A scanner using surface micromachining technology andhaving a mirror that is tilted out of the plane of the fabrication isdescribed in Kiang et al., “Surface-Micromachined Electrostatic-CombDriven Scanning Micromirrors for Barcode Scanners”, Ninth Annual Int.Workshop on Micro Electro Mechanical Systems, San Diego, 1996, pp.192-19997. All of such devices tend to have difficulty in maintainingflatness and smoothness in the mirror elements and may have difficultyin precise static positioning of the mirror due to hysteresis in thecoupling between the electrostatic comb drive actuator in the plane ofthe substrate and the mirror element out of the substrate plane.

[0006] In general, it is an object of the present invention to provide arelatively inexpensive optical microswitch having a small form factor.

[0007] Another object of the invention is to provide an opticalmicroswitch of the above character in which the reflective face of amicromirror rotates in the focal plane of a focusing lens.

[0008] Another object of the invention is to provide an opticalmicroswitch of the above character in which first and secondmicromirrors are closely packed and disposed in the focal plane of afocusing lens.

[0009] Another object of the invention is to provide an opticalmicroswitch of the above character which is capable of coupling visibleor infrared light into an optical fiber with low transmission losses.

[0010] Another object of the invention is to provide an opticalmicroswitch of the above character which has relatively fast switchingtimes.

[0011] Another object of the invention is to provide an opticalmicroswitch of the above character in which the mirror is capable ofangular rotations over a relatively large range.

SUMMARY OF THE INVENTION

[0012] The present invention provides an optical microswitch comprisinga support body and first and second output fibers. A rotaryelectrostatic microactuator is carried by the body and extends in aplane. A micromirror is disposed out of the plane. The microactuator hasa mirror holder coupled to the micromirror and at least one comb driveassembly coupled to the mirror holder for driving the micromirror aboutan axis of rotation extending perpendicular to the plane between a firstposition for reflecting a laser beam to the first output fiber and asecond position for reflecting the laser beam to the second outputfiber.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The accompanying drawings, which are somewhat schematic in manyinstances and are incorporated in and form a part of this specification,illustrate several embodiments of the invention and, together with thedescription, serve to explain the principles of the invention.

[0014]FIG. 1 is a perspective view of an optical microswitch with rotaryelectrostatic microactuator of the present invention.

[0015]FIG. 2 is a plan view of a rotary electrostatic microactuator foruse in the optical microswitch of FIG. 1.

[0016]FIG. 3 is a cross-sectional view of the rotary electrostaticmicroactuator of FIG. 2 taken along the line 3-3 of FIG. 2.

[0017]FIG. 4 is a plan view of another embodiment of a rotaryelectrostatic microactuator for use in the optical microswitch of FIG.1.

[0018]FIG. 5 is a plan view of a further embodiment of a rotaryelectrostatic microactuator for use in the optical microswitch of FIG.1.

[0019]FIG. 6 is a perspective view of another embodiment of an opticalmicroswitch with rotary electrostatic microactuator of the presentinvention.

DESCRIPTION OF THE INVENTION

[0020] Optical microswitch 11, shown schematically in FIG. 1, is formedfrom a support body 12 of any suitable size and shape and made from anysuitable material such as a ceramic material. Body 12 shown in FIG. 1has a base 13 and a back 14 secured to the base and extendingperpendicularly from the base. Support body 12 is optionally coupled toone and as shown a plurality of output optical fibers 16, which can beeither single mode or multi-mode fibers. In this regard, a bundle 21 ofsuch output fibers 16 is secured together by a tube 22 mounted on base13 by any suitable means such as bracket 23. The plurality of opticalfibers 16 includes first and second optical fibers 16 a and 16 b. Tube22 and output bundle 21 terminate at an end 31. A conventional focusinglens such as a GRIN lens 32 is disposed adjacent the end 31 of the fiberoptic output bundle 21 and is mounted to base 13 by any suitable meanssuch as bracket 33. Lens 32 has a sufficient field of view toaccommodate all of fibers 16 in output bundle 21.

[0021] At least one and as shown a plurality of input optical fibers 41can optionally be coupled to support body 13 for providing laser lightto optical microswitch 11. The input optical fibers 41 are arranged in abundle 42 secured together by any suitable means such as tube 43. Inputfibers 41 terminate at respective ends 44. Input bundle 42 is secured tobase 13 by any suitable means such as bracket 46. A conventionalcollimating lens such as GRIN lens 47 is disposed adjacent ends 44 andsecured to base 13 by bracket 48 or any other suitable means. Lens 47 isperpendicular to lens 32. An input laser beam 51 from a laser source(not shown) is directed on a path by one of input optical fibers 41through lens 47 to optical microswitch 11. The glass surfaces of fibers16 and 41 and lenses 32 and 47 are coated in a conventional manner withan anti-reflective material.

[0022] First and second rotary electrostatic microactuators 56 and 57are carried by support body 12 for alternatively coupling input laserbeam 51 into first output fiber 16 a or second output fiber 16 b. Firstplanar microactuator 56 is formed from a first planar rotator chip 58secured to base 13 by any suitable means such as an adhesive (notshown). For simplicity, first microactuator 56 and first rotator chip 58are shown schematically in FIG. 1. The first microactuator 56 ispreferably disposed perpendicular to input laser beam 51 and parallel tothe central longitudinal axis of output of lens 32. A firstmicromachined mirror 61 extends out of the plane of first microactuator56 and is secured to the first microactuator by mean of a post 62preferably formed integral with the micromachined mirror 61. Mirror 61and post 62 are preferably micromachined separately from microactuator56. Post 62 is joined at its base to the microactuator 56 by an adhesive(not shown) or any other suitable means. First mirror 61 has areflective face or surface 63 and is rotatable by first microactuator 56about an axis of rotation 64 extending through post 62 and disposedperpendicular to the plane of first microactuator 56. The axis ofrotation 64 preferably intersects the reflective face 63 of micromirror61 to ensure that face 63 is undergoing pure rotation. In addition, axisof rotation 64 is preferably placed at the focal plane of output lens32.

[0023] Second planar microactuator 57 extends in a second plane and issubstantially identical to first microactuator 56. The secondmicroactuator 57 is formed from a second planar rotator chip 67 mountedto block 14 by any suitable means such as an adhesive (not shown). Forsimplicity, second microactuator 57 and second rotator chip 67 are shownschematically in FIG. 1. Second microactuator 57 is suspended over firstmicroactuator 56 and is disposed perpendicular to the plane of the firstmicroactuator. A second mirror 68 is carried by second microactuator 57and is disposed out of the plane of the microactuator 57. Secondmicromachined mirror 68 is preferably formed with an L-shaped post 71having a base portion or base 71 a and a cantilever portion or extension71 b. Base 71 a is secured to the microactuator 57 by an adhesive (notshown) or any other suitable means. Mirror 68 rotates about an axis ofrotation 72 extending along base 71 a and disposed perpendicular to theplane of second microactuator 57. The axis of rotation 64 of firstmirror 61 and the axis of rotation 72 of second mirror 68 are preferablydisposed in a plane extending perpendicular to the first and secondmicroactuators 56 and 57. The mirrors 61 and 68 each have a sufficientrange of rotation to permit the mirror 61 to direct laser beam 51, bymeans of lens 32, onto the core of each of optical fibers 16. Extension71 b is centered on an axis 73 extending parallel to the plane of secondmicroactuator 57. Axis of rotation 64 of the first microactuator 56 andaxis 73 are preferably disposed in a plane extending perpendicular tothe first microactuator and parallel to the second microactuator. Secondmirror 68 has a reflective face or surface 74 which is thus centered onthe focal plane of lens 32. Reflective surfaces 63 and 74 of respectivemicromirrors 61 and 68 are highly reflective at the particularwavelength of laser beam 51.

[0024] Any suitable micromachined actuator can be utilized for first andsecond microactuators 56 and 57. Several preferred microactuators aredisclosed in copending U.S. patent application Ser. No. ______ filedDec. 15, 1999 [Our File No. A-68185], the entire contents of which isincorporated herein by this reference. One particularly preferred rotaryelectrostatic microactuator 101, shown in FIGS. 2 and 3, is formed on aplanar substrate 102 of the respective rotator chip 58 or 67. Arotatable member or circular mirror holder 103 overlies the substrate102. A plurality of first and second comb drive assemblies 106 and 107are carried by substrate 102 for rotating mirror holder 103 in first andsecond opposite angular directions about an axis of rotation 108extending through the center of the circular mirror holder 103perpendicular to planar substrate 102 and thus FIG. 2. Axis of rotation108 corresponds to axes of rotations 64 and 72 of the respectivemicroactuators 56 and 57. Each of the first and second comb driveassemblies 106 and 107 includes a first comb drive member or comb drive111 mounted on substrate 102 and a second comb drive member or combdrive 112 overlying the substrate 102. First and second spaced-apartsprings 113 and 114 are included in microactuator 101 for supporting orsuspending second comb drives 112 and mirror holder 103 above thesubstrate 102 and for providing radial stiffness to the movable secondcomb drives 112 and thus the mirror holder 103.

[0025] Substrate 102 is made from any suitable material such as siliconand is preferably formed from a silicon wafer. The substrate has athickness ranging from 200 to 600 microns and preferably approximately400 microns. Mirror holder 103, first and second comb drive assemblies106 and 107 and first and second springs 113 and 114 are formed atop thesubstrate 102 by a second or top layer 116 made from a wafer of anysuitable material such as silicon. Top wafer 116 has a thickness rangingfrom 10 to 200 microns and preferably approximately 85 microns and issecured to the substrate 102 by any suitable means. The top wafer 116 ispreferably fusion bonded to the substrate 102 by means of a silicondioxide layer 117 having a thickness ranging from 0.1 to two microns andpreferably approximately one micron. Top wafer 116 may be lapped andpolished to the desired thickness. The mirror holder 103, the first andsecond comb drive assemblies 106 and 107 and the first and secondsprings 113 and 114 are formed from the top wafer 116 by any suitablemeans. Preferably, such structures are etched from wafer 116 using deepreactive ion etching (DRIE) techniques. Mirror holder 103 is spacedabove substrate 102 by an air gap 118, that ranges from three to 30microns and preferably approximately 15 microns, so as to beelectrically isolated from the substrate.

[0026] At least one and preferably a plurality of first comb driveassemblies 106 are included in rotary electrostatic microactuator 101and disposed about axis of rotation 108, shown as a point in FIG. 2, fordriving mirror holder 103 in a clockwise direction about axis 108. Atleast one second comb drive assembly 107 and preferably a plurality ofsecond comb drive assemblies 107 can be included in microactuator 101for driving the mirror holder in a counterclockwise direction about theaxis of rotation 108. Each of the first and second comb drive assemblies106 and 107 extends substantially radially from axis of rotation 108and, in the aggregate, subtend an angle of approximately 180° so as toprovide rotary microactuator 101 with a semicircular or fanlike shapewhen viewed in plan (see FIG. 2). More specifically, microactuator 101has three first comb drive assemblies 106 a, 106 b and 106 c and threesecond comb drive assemblies 107 a, 107 b and 107 c. Rotarymicroactuator 101 has a base 119 extending along a diameter of thesemicircle formed by the microactuator 101 and has an outer radialextremity 121 resembling the arc of a semicircle. Radial extremity 121has first and second ends which adjoin the first and second oppositeends of base 119. The radial extremity 121 is defined by the outerradial extremities of first and second comb drive assemblies 106 and107. Mirror holder 103 and axis of rotation 108 are disposed at thecenter of the semicircle adjacent base 119.

[0027] First and second comb drive assemblies 106 and 107 areinterspersed between each other, that is, a second comb drive assembly107 is disposed between each pair of adjacent first comb driveassemblies 106. The first comb drive assemblies 106 are symmetricallydisposed relative to the second comb drive assemblies 107 about theradial centerline of rotary electrostatic microactuator 101, that is theimaginary line extending in the plane of substrate 102 through axis ofrotation 108 and perpendicular to base 119. Each of the first and secondcomb drive assemblies 106 and 107 has a length ranging from 200 to 2,000microns and more preferably approximately 580 microns. Rotarymicroactuator 101 has a length measured along base 119 ranging from 500to 5,000 microns and more preferably approximately 1,800 microns.

[0028] First comb drive 111 of each of first and second comb driveassemblies 106 and 107 is mounted to substrate 102 by means of silicondioxide layer 117. As such, the first comb drives 111 are immovablysecured to substrate 102. Each of the first comb drives 111 has aradially-extending bar 122 provided with a first or inner radial portion122 a and a second or outer radial portion 122 b. Outer portion 122 bextends to outer radial extremity 121 of microactuator 101. A pluralityof comb drive fingers 123 are longitudinally spaced apart along thelength of bar 122 at a separation distance ranging from eight to 50microns and preferably approximately 24 microns. The comb drive fingers123 extend substantially perpendicularly from bar 122 and are eacharcuate in shape. More specifically, each comb finger 123 has asubstantially constant radial dimension relative to axis of rotation 108as it extends outwardly from the bar 122. Fingers 123 have a lengthranging from approximately 22 to 102 microns and increase substantiallylinearly in length from bar inner portion 122 a to bar outer portion 122b. Although the comb fingers 123 can vary in width along their length,the comb fingers 123 are shown as having a constant width ranging fromtwo to 12 microns and preferably approximately six microns. Bar innerportions 122 a for first comb drive assemblies 106 a and 106 b andsecond comb drive assemblies 107 b and 107 c are joined to a base member124 which serves to anchor such bars 122 to substrate 102 and permitsuch bar inner portions 122 a to thus have a smaller width and therelated comb drives 123 to have a corresponding longer length.

[0029] Second comb drives 112 are spaced above substrate 102 by air gap118 so as to be movable relative to substrate 102 and relative to firstcomb drives 111. The second comb drives 112 have a construction similarto the first comb drives 111 discussed above and, more specifically, areformed with a bar 126 that extends radially outwardly from axis ofrotation 108. The bar 126 has a first or inner radial portion 126 a inclose proximity to axis 108 and a second or outer radial portion 126 bthat extends to radial extremity 121. A plurality of comb drive fingers127 are longitudinally spaced apart along the length of bar 126 and aresubstantially similar to comb fingers 123. Arcuate comb fingers 127 areoffset relative to comb fingers 123 so that the comb fingers 127 onsecond comb drive 112 can interdigitate with comb fingers 123 on firstcomb drive 111 when the second comb drives 112 are rotated about axis108 towards the stationary first comb drives 111. Each of first andsecond comb drive assemblies 106 and 107 resembles a sector of thesemicircular microactuator 101.

[0030] Means including first and second spaced-apart springs 113 and 114are included within rotary electrostatic microactuator 101 for movablysupporting second comb drives 112 over substrate 102. First and secondsuspension elements or springs 113 and 114 each have a length whichpreferably approximates the length of first and second comb driveassemblies 106 and 107, however springs having lengths less than thelength of the comb drive assemblies can be provided. Although first andsecond springs 113 and 114 can each be formed from a single springmember, the springs 113 and 114 are each preferably U-shaped or V-shapedin conformation so as to be a folded spring. As shown, springs 113 and114 are substantially U-shaped. Each of springs 113 and 114 is made fromfirst and second elongate spring members 131 and 132. First or linearspring member 131 has first and second end portions 131 a and 131 b andsecond or linear spring member 132 has first and second end portions 132a and 132 b.

[0031] The first end portion 131 a of each folded spring 113 and 114 issecured at its end to substrate 102 adjacent axis of rotation 108 bymeans of silicon dioxide layer 117 (see FIG. 3). The balance of thespring is spaced above the substrate by air gap 118. Second end portion131 b of each spring 113 and 114 is secured to first end portion 132 aof the second spring member 132. First and second beam-like springmembers 131 and 132 each extend radially outwardly from axis of rotation108 and preferably have a length approximating the length of first andsecond comb drive assemblies 106 and 107. The spring members 131 and 132are preferably approximately equal in length and each have a length ofapproximately 500 microns. As such, spring first end portions 131 a aresecured to substrate 102 adjacent spring second end portions 132 b.Although first end portion 131 a of each spring 113 and 114 can besecured to substrate 102 adjacent mirror holder 103 or adjacent outerradial extremity 121, the first end portion 131 a is preferably securedto substrate 102 adjacent outer radial extremity 121. First and secondspring members 131 and 132 each have a width ranging from one to 10microns and preferably approximately four microns. First and secondthin, elongate sacrificial bars 133 and 134, of a type described in U.S.Pat. No. 5,998,906 and in copending U.S. patent application Ser. No.09/135,236 filed Aug. 17, 1998, the entire contents of each of which areincorporated herein by this reference, extend along each side of eachspring member 131 and 132 for ensuring even etching and thus the desiredrectangular cross section of the spring members. Sacrificial bars 133and 134 are disposed along opposite sides of the spring members andextend parallel to the respective spring member.

[0032] Second end portion 132 b of each spring 113 and 114 is secured toat least one of second comb drives 112. In this regard, first and secondmovable frame members or frames 141 and 142, spaced above substrate 102by air gap 118, are provided in rotary electrostatic microactuator 101.Each of the frames 141 an 142 is substantially U-shaped in conformationand includes as side members bars 126 of the adjoining second combdrives 112. More specifically, first movable frame 141 includes bar 126of second comb drive assembly 107 a, bar 126 of first comb driveassembly 106 a and an arcuate member 143 which interconnects such barouter portions 126 b. Second movable frame 142 is similar inconstruction and includes as side members bar 126 of second comb driveassembly 107 c, bar 126 of first comb drive assembly 106 c and anarcuate member 144 which interconnects such bar outer portions 126 b.Second end portion 132 b of first spring 113 is secured to arcuatemember 143 adjacent to bar outer portion 126 b of second comb driveassembly 107 a, while the second end portion 132 b of second spring 114is secured to arcuate member 144 adjacent bar outer portion 126 b offirst comb drive assembly 106 c. In this manner, first folded spring 113is disposed inside first movable frame 142 and second folded spring 114is disposed inside second movable frame 142. Bar inner portion 126 a ofsecond comb drive assembly 107 a is joined to mirror holder 103 andserves to secure first spring 113 to the mirror holder. Similarly, barinner portion 126 a of first comb drive assembly 106 c is joined tomirror holder 103 for interconnecting second spring 114 to the mirrorholder.

[0033] First and second movable frames 141 and 142 are symmetricallydisposed about the radial centerline of rotary electrostaticmicroactuator 101. At least one comb drive assembly and preferably atleast one first comb drive assembly 106 and at least one second combdrive assembly 107 are disposed between first and second movable frames141 and 142 and thus first and second springs 113 and 114. Morespecifically, first comb drive assemblies 106 a and 106 b and secondcomb drive assemblies 107 b and 107 c are disposed between frames 141and 142. Bar 126 of second comb drive assembly 107 b and bar 126 offirst comb drive assembly 106 b are joined back to back to form a thirdmovable frame 147 preferably extending along the centerline ofmicroactuator 101 between movable frames 141 and 142. An inner arcuatemember or shuttle 148 is joined at opposite ends to first and secondmovable frames 141 and 142. One end of rigid shuttle 148 is secured tobar inner portion 126 a of first comb drive assembly 106 a while thesecond end of the shuttle 148 is secured to bar inner portion 126 a ofsecond comb drive assembly 107 c. Third movable frame 147 is joined tothe middle of the shuttle 148 so as to rotate in unison with first andsecond movable frames 141 and 142 about axis 108. An additional arcuatemember 151 is provided in microactuator 101 for rigidly securingtogether second end portions 131 b of first and second springs 113 and114. The arcuate member 151 overlies substrate 102 and extends at leastpartially around the axis of rotation 108. Member 151 is disposedbetween shuttle 148 and mirror holder 103 and rotates about axis 108free of mirror holder 103. The suspended structures of microactuator101, that is mirror holder 103, second comb drives 112, first and secondsprings 131 and 132 and first and second movable frames 141 and 142,each have a thickness ranging from 10 to 200 microns and preferablyapproximately 85 microns.

[0034] Second comb drives 112 of first and second comb drive assemblies106 and 107 are movable in a direction of travel about axis of rotation108 by means of movable frames 141, 142 and 147 between respective firstpositions, as shown in FIG. 2, in which comb drive fingers 123 and 127of the first and second comb drives are not substantially fullyinterdigitated and respective second positions, not shown, in which thecomb drive fingers 123 and 127 are substantially fully interdigitated.Although comb drive fingers 123 and 127 can be partially interdigitatedwhen second comb drives 112 are in their first positions, the combfingers 123 and 127 are shown as being fully disengaged and thus are notinterdigitated when second comb drives 112 are in their first positions.When in their second positions, comb fingers 127 of second comb drives112 extend between respective comb drive fingers 123 of the first combdrives 111. Comb fingers 127 approach but preferably do not engage bar122 of the respective first comb drives 111 and similarly comb drivefingers 123 approach but preferably do not engage bar 126 of therespective second comb drives 112. Rigid movable frames 141, 142 and 147are constructed as light weight members to decrease the mass and momentof inertia of the movable portions of microactuator 101 and thusfacilitate rotation of second comb drives 112 and mirror holder 103about axis of rotation 108. Each of the movable frames 141, 142 and 147is substantially hollow and formed with a plurality of internal beams ortrusses 152 for providing rigidity to the movable frame.

[0035] Electrical means is included within microactuator 101 for drivingsecond comb drives 112 between their first and second positions. Suchelectrical means includes a controller and voltage generator 161 that iselectrically connected to a plurality of electrodes provided onsubstrate 102 by means of a plurality of electrical leads 162.Controller 161 is shown schematically in FIG. 2. A first groundelectrode 166 and a second ground electrode 167 are formed on substrate102 and are respectively joined to the first end portion 131 a of firstand second springs 113 and 114 for electrically grounding second combdrives 112 and mirror holder 103. Electrodes 166 and 167 serve as theattachment points for spring first end portions 131 a to the substrate102. First comb drives 111 of first comb drive assemblies 106 can besupplied a voltage potential from controller 161 by means of anelectrode 171 electrically coupled to bar outer portion 122 b of firstcomb drive assembly 106 a and an additional electrode 172 electricallycoupled to the first comb drive 111 of first comb drive assembly 106 band to first comb drive 111 of first comb drive assembly 106 c by lead173. An electrode 176 is secured to the first comb drive 111 of secondcomb drive assembly 107 a by means of lead 177 and to second comb driveassembly 107 b and an electrode 179 is joined to bar outer portion 122 bof second comb drive assembly 107 c for providing a voltage potential tothe first comb drives of second comb drive assemblies 107. A metal layer181 made from aluminum or any other suitable material is created on thetop surface of top wafer 116 for creating electrodes 166, 167, 171, 172,176 and 179 and for creating leads 173, 174, 177 and 178 (see FIG. 2).First and second pointers 186 extend radially outwardly from the outerend of third movable frame 147 for indicating the angular position ofmirror holder 103 about axis 108 on a scale 187 provided on substrate102.

[0036] Means in the form of a closed loop servo control can be includedin microactuator 101 for monitoring the position of second comb drives112 and thus mirror holder 103. For example, controller 161 candetermine the position of the movable comb drives 112 by means of aconventional algorithm included in the controller for measuring thecapacitance between comb drive fingers 127 of the movable comb drives112 and the comb drive fingers 123 of the stationary comb drives 111. Asignal separate from the drive signal to the comb drive members can betransmitted by controller 161 to the microactuator for measuring suchcapacitance. Such a method does not require physical contact between thecomb drive fingers. Alternatively, a portion of the output opticalenergy coupled into the output fiber 16 can be diverted and measured andthe drive signal from the controller 161 to the microactuator 101adjusted until the measured optical energy is maximized.

[0037] In operation and use of optical microswitch 11, first and secondmicroactuators 56 and 57 are utilized to respectively rotate first andsecond mirrors 61 and 68 to direct input laser beam 51 to either firstor second output fibers 16 a or 16 b or any of the other optical fibers16 of output bundle 21. Mirror holder 103 of the respectivemicroactuator 101 can be rotated in opposite first and second directionsof travel about axis of rotation 108 by means of controller 161. Theamount of rotation can be controlled by the amount of voltage suppliedto the appropriate first comb drives 111 of the microactuator 101. Asshown in FIG. 1, laser beam 51 is launched by input lens 57 onto thereflective surface 74 of second mirror 68, from which the beam 51 a isreflected onto surface 63 of first mirror 61. Input laser beam 51 b isreflected by the first mirror 61 onto the desired portion of the imageplane of output lens 32 so that the laser beam 51 is focused and coupledby lens 32 into the appropriate optical fiber 16 of output bundle 21.

[0038] Rotation of second mirror 68 in first and second oppositedirections about axis of rotation 72 by second microactuator 57 controlsthe vertical position relative to first microactuator 56 at which thereflected beam 51 a strikes reflective face 63 on the axis of rotation64 of the first mirror 61. Rotation of the first mirror 61 about axis ofrotation 64 by first microactuator 56 controls the horizontal positionrelative to the first microactuator 56 at which the beam 51 b reflectedby the first mirror strikes output lens 32. In this manner, input laserbeam 51 can be directed by the first and second mirrors 61 and 68 intoany one of the optical fibers of output bundle 21. For example, rotationof first micromirror 61 to a first position and rotation of secondmicromirror 68 to a first position reflects the laser beam 51 to firstoutput fiber 16 a, while rotation of first micromirror 61 to a secondposition and rotation of second micromirror 68 to a second positionreflects the laser beam 51 to second output fiber 16 b. The position ofthe mirror holders 103 of microactuators 56 and 57 and thus mirrors 61and 68 can optionally be monitored in the manner discussed above withrespect to microactuator 101. Micromirrors 61 and 68 are each capable ofrotating at speeds less than five milliseconds between fibers 16 withoptical losses of less than one dB.

[0039] In its rest position, second mirror 68 is aligned on secondmicroactuator 57 so its reflective surface 74 is capable of reflectinginput laser beam 51 from the center of input lens 47 onto the center ofthe first mirror 61. Similarly, first mirror 61 is angularly disposedrelative to first microactuator 56 so that when the first mirror is inits rest position, the input beam 51 a impinging the first mirror 61 isreflected by the first mirror onto the center of output lens 32. Suchpositioning of first and second mirrors 61 and 68 relative to first andsecond microactuators 56 and 57 minimizes the rotational travel of themirrors during the operation of optical microswitch 11. The first andsecond mirrors 61 and 68 are each capable of ± six degrees angularrotation, that is a rotation of six degrees in both the clockwise andcounterclockwise directions for an aggregate rotation of twelve degrees.

[0040] The fanlike shape of first and second microactuators 56 and 57permits respective first and second mirrors 61 and 68 to be mountedalong the base 119 of the respective microactuator 101. For example, theplacement of first mirror 61 on such base 119 of first microactuator 56permits the microactuator 56 to be positioned along one side of firstrotator chip 58 and support base 13 so that input laser beam 51 has apath to second mirror 68 that is unobstructed by the microactuator 56.Second mirror 68 overhangs such side of rotator chip 58. Similarly, thefanlike shape of second microactuator 57 permits the microactuator 57 tooverhang first microactuator 56. Second mirror 68 advantageously rotatesabout axis 72 disposed along the base 119 of second microactuator 57 andoverhangs second microactuator 57 so as to be in close proximity tofirst mirror 61. This close placement of first and second mirrors 61 and68 minimizes the length of base 71 a of second mirror post 71 and theoptical path of input laser beam 51.

[0041] The separate fabrication of first and second mirrors 61 and 68allows for larger choice of reflective coatings for the mirrors,including multilayer dielectric mirrors, enhanced metallic mirrors andmetallic mirrors otherwise incompatible with micromachining fabricationsteps such as sacrificial release or high temperature processing. Theseparate mirrors 61 and 68 can be fabricated on relatively thick andvery smooth flat substrates, which is difficult to achieve with anintegrated micromachined process. In addition, mirrors rotating aboveand out of the plane of the substrate 102 allow for novel mechanicallayout and packaging of microswitch 11, particularly the close couplingof microactuators 56 and 57.

[0042] The utilization of rotary electrostatic microactuators, andparticularly electrostatic microactuators having a fanlike shape orother shape that permits the axis of rotation to be placed along a sideof the microactuator, allows the optical microswitch 11 to have arelatively small form factor of less than approximately one cubiccentimeter. Microactuators 56 and 57 desirably require relatively lowpower and permit rapid switching between fibers. Microswitch 11 isparticularly suited for use as an optical switch in a fiber opticnetwork of a telecommunications system. However, the optical microswitch11 can be used in other applications, such as in computer data storagesystems, and more specifically in an optics module of a magneto-opticaldata storage system. Other applications include data networks and cabletelevision systems.

[0043] Although optical microswitch 11 is shown for use with a pluralityof input optical fibers 41, a single input fiber 41 can be provided.Alternative, input laser beam 51 can be supplied from any other suitablesource, such as directly from a laser in close proximity to or mountedon support body 12. In addition, it should be appreciated thatmicroswitch 11 can be bidirectional, that is optical fibers 16 can serveas input fibers and optical fibers 41 can serve as output fibers;

[0044] Another rotary electrostatic microactuator disclosed in copendingU.S. patent application Ser. No. ______ filed Dec. 15, 1999 [Our FileNo. A-68185] and suitable for use as first and/or second microactuators56 and 57 in optical microswitch 11 is shown in FIG. 4. Microactuator201 therein has similarities to microactuator 101 and like referencenumerals have been used to describe like components of microactuators101 and 201. A rotatable member or mirror holder 202 overlies substrate102 of the respective rotator chip 58 or 67. A plurality of first andsecond comb drive assemblies 203 and 204 are carried by the substrate102 for rotating the mirror holder 202 in first and second oppositedirection about an axis of rotation 206 extending perpendicular toplanar substrate 102. Axis of rotation 206 corresponds to axes ofrotations 64 and 72 of the respective microactuators 56 and 57. The axisof rotation is shown as a point in FIG. 4 and labeled by reference line206. Each of the first and second comb drive assemblies 203 and 204includes a first drive member or comb drive 211 mounted on substrate 102and a second comb drive member or comb drive 212 overlying thesubstrate. First and second spaced-apart springs 213 and 214 areincluded in microactuator 201 for supporting or suspending second combdrives 212 and mirror holder 202 above the substrate 102 and forproviding radial stiffness to the second comb drives 212 and the mirrorholder 202. The mirror holder 202, first and second comb driveassemblies 203 and 204 and first and second springs 213 and 214 areformed from top layer 116 by any suitable means such as discussed abovefor microactuator 101. Mirror holder 202, second comb drives 212 andfirst and second springs 213 and 214 are spaced above substrate 102 byair gap 188 and have thicknesses similar to those discussed above forthe like components of microactuator 101.

[0045] At least one and preferably a plurality of first comb driveassemblies 203 are included in rotary electrostatic microactuator 201and disposed about axis of rotation 206 for driving mirror holder 202 ina clockwise direction about axis of rotation 206. At least one andpreferably a plurality of second comb drive assemblies 204 can beincluded in microactuator 201 for driving the mirror holder in acounterclockwise direction about the axis of rotation 206. Each of thefirst and second comb drive assemblies 203 and 204 extends substantiallyradially from axis of rotation 108 and the assemblies 203 and 204, inthe aggregate, subtend an angle of approximately 1800 to provide thesemicircular or fanlike shape to microactuator 201. More particularly,microactuator 201 has four first comb drive assemblies 203 a, 203 b, 203c and 203 d and four second comb drive assemblies 204 a, 204 b, 204 cand 204 d. The first comb drive assemblies 203 are interspersed betweenthe second comb drive assemblies 204. The rotary microactuator 201 has abase 219 substantially similar to base 119 and an outer radial extremity221 substantially similar to outer radial extremity 121. First combdrive assemblies 203 are symmetrically disposed relative to second combdrive assemblies 204 about the radial centerline of rotary electrostaticmicroactuator 201, that is the imaginary line extending in the plane ofsubstrate 102 through axis of rotation 206 perpendicular to base 219.Mirror holder 202 and axis of rotation 206 are disposed at the center ofmicroactuator 201 adjacent base 219. The rotary microactuator has alength measured along base 219 ranging from 500 to 5,000 microns andpreferably approximately 2,000 microns.

[0046] First comb drive 211 of each of first and second comb driveassemblies 203 and 204 is mounted to substrate 101 in the mannerdiscussed above with respect to first comb drives 111. Each of the firstcomb drives 211 has a radial-extending bar 226 provided with a first orinner radial portion 226 a and a second or outer radial portion 226 b.The outer portion 226 b of each first comb drive 211 extends to outerradial extremity 221. A plurality of comb drive fingers 227 arelongitudinally spaced apart along the length of bar 226 at a separationdistance ranging from eight to 50 microns and preferably approximately35 microns. The comb drive fingers 227 extend substantiallyperpendicularly from bar 226 and, like comb drive fingers 123, are eacharcuate in shape. Fingers 227 have a length ranging from 25 to 190microns and increase substantially linearly in length from bar innerportion 226 a to bar outer portion 226 b. Each of the comb drive fingers227 has a proximal portion 227 a and a distal portion 227 b. Theproximal portion 227 a has a width ranging from four to 20 microns andpreferably approximately 10 microns, and the distal portion 227 b has awidth less than the width of proximal portion 227 a and, morespecifically, ranging from two to 12 microns and preferablyapproximately six microns.

[0047] Second comb drives 212 and mirror holder 202 are part of amovable or rotatable frame 231 spaced above substrate 102 by air gap 118so as to be electrically isolated from the substrate and movablerelative to the substrate and first comb drives 211. Frame 231 includesa first arm 232, a second arm 233, a third arm 236 and a fourth arm 237,each of which extend in a substantial radial direction from axis ofrotation 206. First and fourth arms 232 and 237 are symmetricallydisposed relative to the centerline of microactuator 101 and second andthird arms 233 and 236 are also symmetrically disposed relative to suchcenterline. First and fourth arms 232 and 237 are each U-shaped inconformation and formed from first and second bars 241 and 242. Thefirst bar 241 has a first or inner radial portion 241 a in closeproximity to axis 206 and a second or outer radial portion 241 b thatextends to outer radial extremity 221. Similarly, second bar 242 has afirst or inner radial portion 242 a and a second or outer radial portion242 b. Outer radial portions 241 b and 242 b are joined by a base member243 at outer radial extremity 221. Inner radial portion 241 a of thefirst bar 241 is joined to mirror holder 202, while inner radial portion242 a of second bar 242 extends freely adjacent the mirror holder 202.Second and third arms 233 and 236 are joined at their inner portions tomirror holder 202.

[0048] First bar 241 of first arm 232 forms part of second comb drive212 of first comb drive assembly 203 a, while second bar 242 of firstarm 232 serves as part of the second comb drive 212 of second comb driveassembly 204 a. A plurality of comb drive fingers 251 are longitudinallyspaced apart along the length of such first bar 241 for forming the combdrive fingers of first comb drive assembly 203 a, while a plurality ofcomb drive fingers 251 are longitudinally spaced apart along the lengthof second bar 242 of such first arm 232 for forming the comb drivefingers of first comb drive assembly 204 a. Comb drive fingers 251 aresubstantially similar to comb drive fingers 227 and have a first orproximal portion 251 a joined to the respective bar 241 or 242 and asecond or distal portion 251 b extending from such proximal portion 251a. Distal portions 251 b have a width less than the width of proximalportions 251 a. Arcuate comb drive fingers 251 are offset relative tocomb drive fingers 227 so that comb drive fingers 251 can interdigitatewith comb drive fingers 227. First bar 241 of fourth arm 237 similarlyserves as part of second comb drive 212 of second comb drive assembly204 d, while second bar 242 of the fourth arm 237 serves as part of thesecond comb drive 212 for first comb drive assembly 203 d. Comb drivefingers 251 extend from first and second bars 241 and 242 of fourth arm237.

[0049] Second and third arms 233 and 236 are included in second combdrives 212 of first comb drive assemblies 203 b and 203 c and secondcomb drive assemblies 204 b and 204 c. The second arm 233 has a first orinner radial portion 233 a joined to mirror holder 202 and a second orouter radial portion 233 b adjacent outer radial extremity 221. Thirdarm 236 is similar in construction to second arm 233 and has a first orinner radial portion 236 a and a second or outer radial portion 236 b. Afirst plurality of comb drive fingers 251 are longitudinally spacedapart along the length of one side of second arm 233 for forming thesecond comb drive of second comb drive assembly 204 b and a secondplurality of comb drive fingers 251 are longitudinally spaced apartalong the length of the other side of second arm 233 for forming thesecond comb drive of first comb drive assembly 203 b. Similarly, a firstplurality of comb drive fingers 251 are longitudinally spaced apartalong one side of third arm 236 for forming second comb drive 212 offirst comb drive assembly 203 c and a second plurality of comb drivefingers 251 are longitudinally spaced apart along the opposite side ofthe third arm 236 for forming second comb drive 212 of second comb driveassembly 204 c. The second and third arms 233 and 236 can optionally bejoined by a link 252 at the respective inner radial portions 233 and 236a for enhancing the rigidity of the arms 233 and 236.

[0050] Means including first and second spaced-apart springs 213 and 214are included within rotary electrostatic microactuator 201 for movablysupporting mirror holder 202 and second comb drives 212 over substrate102. Springs 213 and 214 are symmetrically disposed about the centerlineof microactuator 201 and preferably have a length which approximates thelength of at least some of first and second comb drive assemblies 203and 204. Base 219 of microactuator 201 includes an attachment or bracketmember 253 which has a portion intersecting axis of rotation 206 andserves to secure first and second springs 213 and 214 to substrate 102.Each of the springs 213 and 214 is formed from a single beam-like springmember 256 having a first or inner radial end portion 256 a joined atits end to bracket member 253 and a second or outer radial end portion256 b joined to base member 243 of the respective first arm 232 orfourth arm 237. More specifically, first spring 213 extends from bracketmember 253 up the center of first arm 232 for joinder to the center ofbase member 243. Second spring 214 extends from bracket member 253radially outwardly through the center of fourth arm 237 for joinder tothe center of base member 243. Inner end portions 256 a of springmembers 256 are joined to the bracket member 253 at axis of rotation206. The spring members 256 have a width ranging from one to 10 micronsand preferably approximately four microns. Respective first and fourtharms 232 and 237 serve to secure outer end portions 256 b of the firstand second springs 213 and 214 to mirror holder 202.

[0051] At least one comb drive assembly and preferably at least onefirst comb drive assembly 203 and at least one second comb driveassembly 204 is disposed between first and second springs 213 and 214.More specifically, first comb drive assemblies 203 b and 203 c andsecond comb drive assemblies 204 b and 204 c, each of which is formed inpart by second and third arms 233 and 236, are angularly disposedbetween first and second springs 213 and 214. Additionally, first combdrive assembly 203 a and second comb drive assembly 204 d, symmetricallydisposed relative to each other about the centerline of microactuator201, are angularly disposed between first and second springs 213 and214.

[0052] Comb drive fingers 227 and 251 of first and second comb drives211 and 212 are not substantially fully interdigitated when in theirfirst or rest positions shown in FIG. 4. Although the term notsubstantially fully interdigitated is broad enough to cover comb drivefingers which are not interdigitated when in their rest positions, suchas comb drive fingers 123 and 127 of microactuator 101 shown in FIGS. 2and 3, such term also includes comb drive fingers which are partiallyinterdigitated when in their rest positions. In microactuator 201,distal portions 227 b and 251 b of the comb drive fingers aresubstantially interdigitated when the comb drives 211 and 212 are intheir at rest positions.

[0053] At least one and as shown all of first and second comb driveassemblies 203 and 204 are not centered along a radial extendingoutwardly from axis of rotation 206. In this regard, distal ends 261 ofcomb drive fingers 227 for each comb drive assembly 203 or 204 arealigned along an imaginary line that does not intersect axis of rotation206 and, as such, is spaced-apart from the axis 206. Similarly, distalends 262 of comb fingers 251 extend along an imaginary line which doesnot intersect axis of rotation 206. Each of first and second comb driveassemblies 203 and 204 thus resembles a sector of a semicircle that isoffset relative to a radial of such semicircle.

[0054] Second comb drives 212 of first and second comb drive assemblies203 and 204 are each movable in a direction of travel about axis ofrotation 206 between a first or rest position, as shown in FIG. 4, inwhich comb drive fingers 227 and 251 are not substantially fullyinterdigitated and a second-position (not shown) in which comb drivefingers 227 and 251 are substantially fully interdigitated such asdiscussed above with respect to comb fingers 123 and 127 ofmicroactuator 101. Second comb drives 212 of first comb drive assemblies203 are in their second positions when second comb drives 212 of secondcomb drive assemblies 204 are in their first positions and, similarly,the second comb drives 212 of assemblies 204 are in their secondpositions when the second comb drives 212 of assemblies 203 are in theirfirst positions.

[0055] Electrical means is included within microactuator 201 for drivingsecond comb drives 212 between their first and second positions. Suchelectrical means can include a controller and voltage generator 161electrically connected to a plurality of electrodes provided on thesubstrate 102 by means of a plurality of electrical leads 162. Forsimplicity, controller 161 and leads 162 are not shown in FIG. 4. Suchelectrodes, each of which is substantially similar to the electrodesdiscussed above with respective to microactuator 101, include a commonelectrode 266 electrically coupled by lead 267 to bracket member 253, atleast one drive electrode 271 coupled directly or by means of lead 272to first comb drive 211 of first comb drive assemblies 203 and one ormore drive electrodes 273 coupled directly or by means of lead 274 tofirst comb drives 211 of second comb drive assemblies 204. Several leads274 extending out of the plane of microactuator 201 are shown in phantomlines in FIG. 4. The position of mirror holder 202 and thus mirrors 61and 68 can optionally be monitored in the manner discussed above withrespect to microactuator 101.

[0056] The rotary electrostatic microactuators of microswitch 11 canutilize other than radially-extending comb drive assemblies. Anexemplary push-pull microactuator using coupled linear electrostaticmicromotors is described in copending U.S. patent application Ser. No.______ filed Dec. 15, 1999 [Our File No. A-68185] and shown in FIG. 5.Rotary electrostatic microactuator 401 therein is similar in certainrespects to microactuators 101 and 201 and like reference numerals havebeen used to describe like components of the microactuators 101, 201 and401. The microactuator 401 includes a rotatable member 402 comprising amirror holder, for mounting to the microactuator 401 a micromirror 403extending out of the plane of microactuator 401, and a T-shaped bracket404 secured to micromirror 403. The profile of micromirror 403 is shownin FIG. 5. The rotatable member 402 rotates about an axis of rotation406 extending perpendicular to planar substrate 102 of the respectiverotator chip 68 or 67. Axis of rotation 406 corresponds to axes ofrotations 64 and 72 of the respective microactuators 56 and 57. The axisof rotation 406 intersects micromirror 403 at its reflective surface 403a and is identified as a point by reference numeral 406 in FIG. 5.Microactuator 401 is provided with at least one side 407 and rotatablemember 402 is disposed adjacent the side 407. The microactuator 401 hasfirst and second linear micromotors 408 and 409 and first and secondcouplers 411 and 412 for respectively securing first and secondmicromotors 408 and 409 to bracket 404.

[0057] First and second micromotors 408 and 409 are substantiallyidentical in construction and are formed atop the substrate 102 fromupper layer 116. The micromotors each includes at least one comb driveassembly and preferably includes at least one first comb drive assembly416 and at least one second comb drive assembly 417. As shown, each ofthe micromotors 408 and 409 includes a plurality of four first combdrive assemblies 416 and a plurality of four second comb driveassemblies 471 aligned in parallel. First comb drive assemblies 416 aredisposed side-by-side in a group and second comb drive assemblies 417are similarly disposed side-by-side in a group. The group of assemblies416 are disposed in juxtaposition to the group of assemblies 417.

[0058] Comb drive assemblies 416 and 417 can be of any suitable type. Inone preferred embodiment, the comb drive assemblies are similar to thecomb drive assemblies described in U.S. Pat. No. 5,998,906 issued Dec.7, 1999 and in copending U.S. patent application Ser. No. 09/135,236filed Aug. 17, 1998. The comb drive assemblies 416 and 417 are eachprovided with a first comb drive member or comb drive 421 mounted onsubstrate 102 and a second comb drive 422 overlying the substrate. Firstcomb drives 421 are each formed from an elongate bar 426 having firstand second end portions 426 a and 426 b. A plurality of linear combdrive fingers 427, shown as being linear, are secured to one side of thebar in longitudinally spaced-apart positions along the length of thebar. Comb drive fingers or comb fingers 427 extend perpendicularly frombar 426 and, as shown, can be of equal length and have a constant widthalong their length. Second comb drives 422 are similar in constructionto first comb drives 421 and are each formed from a bar 431 having firstand second end portions 431 a and 43 lb. A plurality of linear combfingers 432, shown as being linear, extend from one side of the bar 431in longitudinally spaced-apart positions. Comb fingers 432 aresubstantially identical to comb fingers 427, but are offset relative tothe comb fingers 427. When comb drive assemblies 416 and 417 are intheir home or rest positions, comb fingers 427 and 432 are notsubstantially fully interdigitated and, preferably, are partiallyinterdigitated as shown in FIG. 5.

[0059] An elongate member or shuttle 436 is included in each of firstand second micromotors 408 and 409. Shuttle 436 has first and second endportions 436 a and 436 b. First end portion 431 a of each of bars 431 issecured to shuttle 436 so that bars 431 extend perpendicularly from oneside of the shuttle 436 between shuttle end portions 436 a and 436 b.

[0060] First and second spaced-apart spring members 437 and 438 areincluded in each of micromotors 408 and 409. Springs 437 and 438 can beof any suitable type and are preferably formed from at least oneelongate beam-like member. In one preferred embodiment, springs 437 and438 each consist of a single such beam-like member similar to firstspring member 131 and to second spring member 132 discussed above.Springs 437 and 438 are substantially identical in construction and eachinclude first and second sacrificial bars 133 and 134 disposed alongopposite sides of the springs for the purposes discussed above. Firstspring 437 has first and second end portions 437 a and 437 b and secondspring 438 has first and second end portions 438 a and 438 b. The springsecond end portion 437 b is secured to shuttle first end portion 436 aand the spring second end portion 438 b is secured to shuttle second endportion 436 b. As a result, at least one and as shown all of first andsecond comb drive assemblies 416 and 417 are disposed between first andsecond springs 437 and 438. The springs 437 and 438 preferably extendperpendicular to shuttle 436 when comb drive assemblies 416 and 417 arein their home or rest positions. Each of the first and second springs437 and 438 preferably has a length approximating the length of combdrive assemblies 416 and 417 so that first end portions 437 a and 438 aare disposed adjacent the second end portions 426 b and 431 b of thecomb drive bars 426 and 431. An attachment block 439 is secured tosubstrate 102 for each spring 437 and 438 and serves to attach the firstend portions 437 a and 438 a of the first and second springs to thesubstrate 102.

[0061] Second comb drives 422, shuttle 436 and first and second springs437 and 438 are spaced above substrate 102 by air gap 118 so as to beelectrically isolated from the substrate and movable relative to thesubstrate. These structures can have any suitable thickness andpreferably each have a thickness ranging from 10 to 200 microns and morepreferably approximately 85 microns. First and second springs 437 and438 are included within the means of microactuator 401 for suspendingand movably supporting second comb drives 422 over substrate 102.

[0062] The second comb drives 422 are movable in a linear direction oftravel relative to first comb drives 421 between first positions, asshown in FIG. 5, in which comb fingers 427 and 432 are not substantiallyfully interdigitated and second positions in which the comb fingers 427and 432 are substantially fully interdigitated. When in their secondpositions, comb fingers 432 extend between respective comb fingers 427and approach but preferably do not engage first comb drive bar 426.Second comb drive members 422 of first comb drive assemblies 416 are intheir second positions when second comb drives 422 of second comb driveassemblies 417 are in their first positions. Conversely, the second combdrives of first comb drive assemblies 416 are in their first positionswhen the second comb drives of second comb drive assemblies 417 are intheir second positions.

[0063] The movement of second comb drives 422 to their first and secondpositions causes shuttle 436 to move in opposite first and second lineardirections relative to substrate 102. Such directions of travel aresubstantially perpendicular to the disposition of the elongate first andsecond comb drive assemblies 416 and 417. A plurality of first stops 441are secured to substrate 102 for limiting the travel of second combdrives 422 of first comb drive assemblies 416 towards their respectivefirst comb drives 421. A plurality of similar second stops 442 aresecured to the substrate for limiting the travel of second comb drives422 of second comb drive assemblies 417 towards their respective firstcomb drives 421. In one preferred embodiment, first and secondmicromotors 408 and 409 are disposed in juxtaposition so that respectiveshuttles 436 are disposed side-by-side in parallel with each other.Second end portions 436b of the shuttles 436 each generally pointtowards micromirror 403 and are centered relative to axis of rotation406.

[0064] First and second couplers 411 and 412 are suspended abovesubstrate 102 by air gap 118 and have a first end secured to shuttlesecond end portion 436b and a second end secured to the bracket 404. Thecouplers 411 and 412 are preferably symmetrically disposed relative toeach other with respect to axis of rotation 406. First coupler 411secures shuttle 436 of the first micromotor 408 to one side of bracket404 and second coupler 412 secures second micromotor 409 to the otherside of bracket 404. In one preferred embodiment, each of the first andsecond couplers has at least one spring member or coupling spring toprovide a non-rigid connection between the shuttle 436 and the bracket404. In a particular preferred embodiment, each of the first and secondcouplers 411 and 412 includes a rigid strip 446 secured at one end toshuttle 436 by means of a first coupling spring 437 and secured at itsother end to bracket 404 by a second coupling spring 448.

[0065] Electrical means is included within microactuator 401 for drivingsecond comb drives 422 of the first and second micromotors 408 and 409between their first and second positions. Such electrical means includesa suitable controller and voltage generator such as controller andvoltage generator 161 electrically coupled to a plurality of electrodesby means of a plurality of electrical leads 162. For simplicity,controller 161 and leads 162 are not shown in FIG. 5. Such electrodes,each of which is substantially similar to the electrodes described abovewith respect to microactuator 101, include first and second groundelectrodes 453 which are electrically coupled by means of respectiveleads 454 to attachment block 439 for first springs 437 so as toelectrically ground first and second springs 437 and 438, shuttle 436and second comb drives 422 of each of the micromotors 408 and 409. Afirst drive electrode 457 is electrically coupled, either directly or bymeans of leads 458, to first comb drives 421 of the first comb driveassemblies 416 of each micromotor 409 and 409. A second drive electrode461 is electrically coupled, either directly or by means of lead 462, tothe first comb drives 421 of the second comb drive assemblies 417 of themicromotors 408 and 409. An additional stop 463 secured to substrate 102can additionally be provided for each micromotor 408 and 409 to limitthe forward travel of shuttle 436 towards rotatable member 402. Theposition of rotatable member 402 and thus mirrors 61 and 68 canoptionally be monitored in the manner discussed above with respect tomicroactuator 101.

[0066] Other optical microswitches utilizing rotary electrostaticmicroactuators can be provided. Optical microswitch 501 shown in FIG. 6is formed from a support body 502 of any suitable size and shape andmade from any suitable material such as a ceramic material. Support body502 has a base 503 and is preferably coupled to a plurality of opticalfibers. As shown in FIG. 6, a plurality of five optical fibers 506 arecoupled to base 503 by any suitable means such as block 507. The fibers506 include an input fiber 506 a and a plurality of output fibers whichcan be any of the fibers 506. First and second output fibers 506 b and506 c are identified in FIG. 6. The optical fibers 506 are secured to aplanar surface 508 of block 507 by any suitable means such as anadhesive (not shown). Fibers 506 extend parallel to each other and arepreferably arranged in juxtaposition on surface 508 with respective endsurfaces 511 linearly aligned across the block 507. Input fiber 506 a ispreferably at the center of fibers 506. A conventional collimating andfocusing lens such as GRIN lens 512 is disposed adjacent end surfaces511 of optical fibers 506 and is mounted on base 503 by any suitablemeans such as an adhesive (not shown). Lens 512 has a sufficient fieldof view to accommodate all of fibers 506. The glass surfaces of fibers506 and lens 512 are coated in a conventional manner with ananti-reflective material. An input laser beam 516 is directed from inputfiber 506 a along a path.

[0067] A rotary electrostatic microactuator 521 is carried by supportbody 502 for directing input laser beam 516 to first output fiber 506 b,second output fiber 506 c or any of the other fibers 506. Microactuator521 is formed from a planar rotator chip 522 secured to base 503 by anysuitable means such as an adhesive (not shown). For simplicity,microactuator 521 and rotator chip 522 are shown schematically in FIG.6. The microactuator 521 is disposed on base 503 such that the plane ofthe microactuator is parallel to input laser beam 516. Microactuator 521is fanlike in shape and is arranged on support body 502 such that thediametric base 523 of microactuator 521, corresponding for example tobase 119 of microactuator 101, is disposed adjacent lens 512 andperpendicular to input laser beam 516. A micromachined mirror 526substantially similar to first mirror 61 discussed above is included inoptical microswitch 501. Micromachined mirror 526 extends out of theplane of microactuator 521 and is secured to the microactuator by meansof a post 527 preferably formed integral with micromirror 526. Post 527is joined at its base to microactuator 521 by an adhesive (not shown) orany other suitable means. Micromirror 526 has a reflective face orsurface 528 rotatable by microactuator 521 about an axis of rotation 529extending through post 527 and disposed perpendicular to the plane ofmicroactuator 521 and to input beam 516. Axis of rotation 529 ispreferably disposed at the focal plane of lens 512 and mirror 526 has asufficient range of rotation to permit the mirror to direct output beam531, by means of lens 512, onto the core of each of optical fibers 506.

[0068] Any suitable micromachined actuator can be utilized formicroactuator 521, including any of the microactuators disclosed incopending U.S. patent application Ser. No. ______ filed Dec. 15, 1999[Our File No. A-68185] and any of such microactuators 101, 201 and 401discussed above.

[0069] In operation and use, microactuator 521 is utilized to rotatemicromirror 526 to reflect input laser beam 516 and cause the outputlaser beam 531 to impinge the image plane of lens 512 for coupling intofirst or second output optical fibers 506 b or 506 c. Rotation ofmicromirror 526 about axis of rotation 529 controls the position atwhich output laser beam 531 impinges lens 512 and thus the optical fiber506 into which output beam 531 is directed. In its rest position,micromirror 526 is preferably aligned on microactuator 521 so that itsreflective surface 528 is parallel with base 523 of the microactuator521. Additionally, as disclosed above, it is preferable that input fiber506 a be one of the centermost optical fibers 506. Such centraldisposition of input fiber 506 a and the disposition of micromirror 526parallel to base 528 minimizes the rotational travel of the micromirrorwhen directing the output beam 521 to the desired output fiber 506. Forexample, micromirror 526 need be rotated only slightly in the clockwisedirection for directing output laser beam 531 into first output fiber506 b. Similarly, slight counterclockwise rotation of micromirror 526about axis 529 results in output laser beam 531 being directed intosecond output fiber 506 c, as shown in FIG. 6. In addition, use of thecentral fiber 506 as the input fiber facilitates the input beam 516impinging reflective surface 528 on the axis of rotation of micromirror526. Micromirror 526 is capable of ±six degrees angular rotation, thatis a rotation of six degrees in both the clockwise and counterclockwisedirections for an aggregate rotation of twelve degrees, althoughapproximately ±four degrees or less of angular rotation is sufficient inmicroswitch 501.

[0070] The disposition of axis of rotation 529 adjacent the base 523 ofmicroactuator 521 facilitates placement of the reflective face 528 ofmicromirror 526 in the focal plane of lens 512. Bidirectional opticalmicroswitch 501 has a relatively small form factor of less thanapproximately one cubic centimeter. The microswitch 501 is suitable foruse in a fiber optic network of a telecommunications system, but canalso be used in other applications such as in a computer data storagesystem.

[0071] As can be seen from the foregoing, a relatively inexpensiveoptical microswitch having a small form factor has been provided. Themicroswitch has a micromirror with a reflective face that rotates in thefocal plane of a focusing lens. The microswitch can optionally beprovided with first and second micromirrors that are closely packed anddisposed in the focal plane of a focusing lens. The microswitch iscapable of coupling visible light into a single mode or multi-modeoptical fiber with low transmission losses and has relatively fastswitching times. The mirror of the microswitch is capable of angularrotations over a relatively large range.

What is claimed is:
 1. An optical microswitch for use with a laser beamcomprising a support body, first and second output fibers carried by thebody, a rotary electrostatic microactuator carried by the body andextending in a plane, a micromirror disposed out of the plane, themicroactuator having a mirror holder coupled to the micromirror and atleast one comb drive assembly coupled to the mirror holder for drivingthe micromirror about an axis of rotation extending perpendicular to theplane between a first position for reflecting the laser beam to thefirst output fiber and a second position for reflecting the laser beamto the second output fiber.
 2. An optical microswitch as in claim 1wherein the microactuator has at least one first comb drive assemblycoupled to the mirror holder for driving the micromirror in a firstdirection of travel about the axis of rotation and at least one secondcomb drive assembly coupled to the mirror holder for driving themicromirror in an opposite second direction about the axis of rotation.3. An optical microswitch as in claim 2 wherein the microactuator has asubstantially planar substrate and the mirror holder overlies thesubstrate, the at least one first comb drive assembly and the at leastone second comb drive assembly each extending substantially radiallyfrom the axis of rotation and each having first and second comb drivemembers, the first comb drive member being mounted on the substrate andthe second comb drive overlying the substrate, each of the first andsecond comb drive members being provided with arcuate comb drivefingers, the second comb drive member being movable in a direction oftravel about the axis of rotation between a first position in which thecomb drive fingers of the first and second comb drive members are notsubstantially fully interdigitated and a second position in which thecomb drive fingers of the first and second comb drive members aresubstantially fully interdigitated.
 4. An optical microswitch as inclaim 3 wherein the microactuator has first and second spaced-apartsprings extending substantially radially from the axis of rotation, theat least one first comb drive assembly and the at least one second combdrive assembly being disposed between the first and second springs, eachof the first and second springs having a first end portion secured tothe substrate and a second end portion secured to the second comb drivemembers for suspending the second comb drive members and the rotatablemember over the substrate.
 5. An optical microswitch as in claim 4wherein each of the first and second springs is a folded spring.
 6. Anoptical microswitch as in claim 3 wherein microactuator has a pluralityof first comb drive assemblies and a plurality of second comb driveassemblies disposed about the axis of rotation and in the aggregatesubtending an angle of approximately 180° about the axis of rotation toform a semicircle having a base extending substantially along a diameterof the semicircle, the axis of rotation being disposed adjacent the baseat the center of the semicircle.
 7. An optical microswitch as in claim 1wherein the microactuator has a substantially planar substrate and firstand second linear micromotors, each of the first and second micromotorshaving first and second spaced-apart springs and at least one comb driveassembly, the at least one comb drive assembly having first and secondcomb drive members, he first comb drive member being mounted on thesubstrate, each of the first and second springs having a first endportion secured to the substrate and a second end portion secured to therespective second comb drive member for suspending the second comb drivemember over the substrate, each of the first and second comb drivemembers being provided with comb drive fingers, the second comb drivemember being movable in a linear direction of travel relative to thefirst comb drive member between a first position in which the comb drivefingers of the first and second comb drive members are not substantiallyfully interdigitated and a second position in which the comb drivefingers of the first and second comb drive members are substantiallyfully interdigitated, a first coupler for securing the second comb drivemember of the first micromotor to the micromirror and a second couplerfor securing the second comb drive member of the second micromotor tothe micromirror whereby movement of the second comb drive members of thefirst and second micromotors to the second position causes themicromirror to rotate about the axis of rotation.
 8. An optical switchas in claim 7 wherein the at least one comb drive assembly of each ofthe first and second micromotors is disposed between the first andsecond springs.
 9. An optical switch as in claim 7 wherein the first andsecond micromotors are symmetrically disposed about the mirror holder.10. An optical microswitch as in claim 1 wherein first and second ofsuch microactuators are carried by the body, the plane of the firstmicroactuator being perpendicular to the plane of the secondmicroactuator whereby rotation of the micromirror of the firstmicroactuator to the first position and rotation of the micromirror ofthe second microactuator to the first position reflects the laser beamto the first output fiber and rotation of the micromirror of the firstmicroactuator to the second position and rotation of the micromirror ofthe second microactuator to the second position reflects the laser beamto the second output fiber.
 11. An optical microswitch as in claim 10wherein the axis of rotation of the first microactuator and the axis ofrotation of the second microactuator are disposed in a plane.
 12. Anoptical microswitch as in claim 1 further comprising closed loop servocontrol means for monitoring the position of the micromirror.
 13. Anoptical microswitch for use with a laser beam comprising a support body,first and second output fibers carried by the body, first and secondrotary electrostatic microactuators carried by the body, the firstmicroactuator extending in a first plane and the second rotarymicroactuator extending in a second plane disposed perpendicular to thefirst plane, each of the first and second microactuators having amicromirror disposed out of the plane of the microactuator and having amirror holder coupled to the micromirror and first and second comb driveassemblies coupled to the micromirror for driving the micromirror aboutan axis of rotation extending perpendicular to the plane between firstand second positions whereby rotation of the micromirror of the firstmicroactuator to the first position and rotation of the micromirror ofthe second microactuator to the first position reflects the laser beamto the first output fiber and rotation of the micromirror of the firstmicroactuator to the second position and rotation of the micromirror ofthe second microactuator to the second position reflects the laser beamto the second output fiber.
 14. An optical microswitch as in claim 13wherein the axis of rotation of the first microactuator and the axis ofrotation of the second microactuator are disposed in a plane.
 15. Anoptical microswitch as in claim 13 wherein each of the first and secondmicroactuators has a plurality of first comb drive assemblies and aplurality of second comb drive assemblies disposed about the axis ofrotation of the microactuator and in the aggregate subtending an angleof approximately 180° about the axis of rotation to form a semicirclehaving a base extending substantially along a diameter of thesemicircle, the axis of rotation being disposed adjacent the base at thecenter of the semicircle.